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Original question:

UCC5870-Q1: AI input clamp

UCC5870-Q1: Vref drive capability?

Shangjian Dai
Prodigy 30 points
Part Number: UCC5870-Q1

Hi,

I am wondering if the pin Vref can be used as a voltage source to power a resistor-NTC circuit, which requires less than 1mA? What is the drive capability of the Vref? Thanks.

Best Regards,

Shangjian

  • 0
    TI__Genius 13760 points

    Hi Shangjian,

    Vref can take loads up to 5mA. Additionally I would recommend using one of the AIx ADC pins for NTC temperature sensing. Three of these pins (AI1, AI3, and AI5) have an internal current source that can be enabled to bias such NTC temperature sensing circuits. This current source is configurable through SPI and can source 0.1mA, 0.3mA, 0.6mA or 1mA.

    You can read more about our integrated ADC starting in section 7.3.3 of the UCC5870-Q1 datasheet.

    Best regards,

    Andy Robles

  • 0
    Prodigy 30 points

    HI Andy,

    Thank you for the answer and the suggestion.  I assume you are referring to NTC diode. While as I am using a NTC thermal resistor, I simply configure AI pins as voltage sensing mode.  Is this application of Vref and AI pins suggested?

    Best Regards,

    Shangjian 

  • +1 in reply to Shangjian Dai
    TI__Genius 10652 points
    Shangjian Dai said:

    Thank you for the answer and the suggestion.  I assume you are referring to NTC diode. While as I am using a NTC thermal resistor, I simply configure AI pins as voltage sensing mode.  Is this application of Vref and AI pins suggested?

    Shangjian, 

    Even for NTC resistor, you would still use the internal current source to bias it. 

    The AIx pins are always in voltage sensing mode because they are ADC inputs. The configurable part is the current level that sources from the pin in order to get a voltage acorss the NTC resistor that the internal ADC can then read. 

    Configuration is like Andy stated in the last post. 

    Best

    DImitri